The invention relates to new photosensitive optically variable (POV) inks, and more particularly, to water soluble POV inks capable of printing images having improved OCR readability due to improved infrared absorption properties.
The POV inks of the invention are effective for use with inkjet printing and have a range of security applications. They can produce security markings of a type which set them apart from other inks. POV inks present a significant challenge to counterfeiting when available from a secure source or licensed supplier, and are often required to be read by OCR readers which suffer in accuracy due to infrared light. The invention provides inkjet inks having the security features of POV inks while having improved OCR processing by laser-based systems widely in use.
The inks of the invention are photosensitive optically variable, meaning that they can provide a printed visually black or dark gray machine-readable information-bearing marking that fluoresces in a specific wavelength range when excited with a shorter wavelength light. The printed images exhibit visual light absorption throughout the entire visual spectrum including the red region of the visible spectrum where red inks are invisible to typical automatic scanning systems. Inks of this type are described, for example by U.S. Patent Publication No. 2003/0041774, U.S. Patent Publication No. 2002/0195586, commonly-assigned, copending U.S. patent application No. Ser. No. 10/873,319 entitled, Photosensitive Optically Variable Ink Compositions Useful for Ink Jet Printing, filed on equal date with this application, in the name of Judith D. Auslander, and commonly-assigned, copending U.S. patent application No. Ser. No. 10/873,321 entitled, Signature Protected Photosensitive Optically Variable Ink Compositions and Process, filed on equal date with this application, in the name of J. D. Auslander and M. Chen. These inks will achieve acceptable PCS (Print Contrast Signal) on virtually all conventional substrates, including dark papers such as Kraft or Manila. The term PCS refers to the ratio of the Print Reflectance Difference (PRD) and the substrate reflectance, and the PRD is the difference between the paper reflectance and ink reflectance. These and other postal terms are given their meanings as defined by the United States Postal Service (USPS). These inks can be used with automated detectors of various types of information-bearing tickets, tags, labels, postage indicia and similar security markings.
There is a need for additional POV inks that provide effective security with improved OCR readability due to improved infrared absorption properties.